OpenGLES.APPLE_texture_format_BGRA8888

OpenGL ES的扩展: APPLE_texture_format_BGRA8888

http://www.khronos.org/registry/gles/extensions/APPLE/APPLE_texture_format_BGRA8888.txt

This extension introduces BGRA_EXT as an acceptable external format.  

This avoids byte swizzling when loading RGBA internal format

textures, which may be stored in BGRA order internally.